implement infinite worlds with threaded chunk generation

Sources/Voxelotl/CMakeLists.txt

@@ -53,6 +53,7 @@ add_executable(Voxelotl MACOSX_BUNDLE
 
   # Game logic classes
   Chunk.swift
+  ChunkGeneration.swift
   WorldGenerator.swift
   CubeMeshBuilder.swift
   ChunkMeshBuilder.swift

Sources/Voxelotl/ChunkGeneration.swift

@@ -0,0 +1,92 @@
+import Foundation
+
+public struct ChunkGeneration {
+  private let queue: OperationQueue
+  private let localReadyChunks = ConcurrentDictionary<SIMD3<Int>, Chunk>()
+  private var generatingChunkSet = Set<SIMD3<Int>>()
+
+  weak var world: World?
+
+  init(queue: DispatchQueue) {
+    self.queue = OperationQueue()
+    self.queue.underlyingQueue = queue
+    self.queue.maxConcurrentOperationCount = 8
+    self.queue.qualityOfService = .userInitiated
+  }
+
+  public mutating func generate(chunkID: SIMD3<Int>) {
+    if !generatingChunkSet.insert(chunkID).inserted {
+      return
+    }
+
+    self.queueGenerateJob(chunkID: chunkID)
+  }
+
+  func queueGenerateJob(chunkID: SIMD3<Int>) {
+    self.queue.addOperation {
+      guard let world = self.world else {
+        return
+      }
+      let chunk = world.generateSingleChunkUncommitted(chunkID: chunkID)
+      self.localReadyChunks[chunkID] = chunk
+    }
+  }
+
+  public mutating func generateAdjacentIfNeeded(position: SIMD3<Float>) {
+    guard let world = self.world else {
+      return
+    }
+    let centerChunkID = World.makeID(position: position)
+    for offset in ChunkGeneration.chunkGenerateNeighbors {
+      let chunkID = centerChunkID &+ offset
+      if world.getChunk(id: chunkID) == nil {
+        self.generate(chunkID: chunkID)
+      }
+    }
+  }
+
+  public mutating func acceptReadyChunks() {
+    guard let world = self.world else {
+      return
+    }
+
+    if self.generatingChunkSet.isEmpty {
+      return
+    }
+
+    for (chunkID, chunk) in self.localReadyChunks.take() {
+      world.addChunk(chunkID: chunkID, chunk: chunk)
+      self.generatingChunkSet.remove(chunkID)
+    }
+  }
+
+  private static let chunkGenerateNeighbors: [SIMD3<Int>] = [
+      SIMD3<Int>(-1, -1, -1),
+      SIMD3<Int>(0, -1, -1),
+      SIMD3<Int>(1, -1, -1),
+      SIMD3<Int>(-1, 0, -1),
+      SIMD3<Int>(0, 0, -1),
+      SIMD3<Int>(1, 0, -1),
+      SIMD3<Int>(-1, 1, -1),
+      SIMD3<Int>(0, 1, -1),
+      SIMD3<Int>(1, 1, -1),
+      SIMD3<Int>(-1, -1, 0),
+      SIMD3<Int>(0, -1, 0),
+      SIMD3<Int>(1, -1, 0),
+      SIMD3<Int>(-1, 0, 0),
+      SIMD3<Int>(0, 0, 0),
+      SIMD3<Int>(1, 0, 0),
+      SIMD3<Int>(-1, 1, 0),
+      SIMD3<Int>(0, 1, 0),
+      SIMD3<Int>(1, 1, 0),
+      SIMD3<Int>(-1, -1, 1),
+      SIMD3<Int>(0, -1, 1),
+      SIMD3<Int>(1, -1, 1),
+      SIMD3<Int>(-1, 0, 1),
+      SIMD3<Int>(0, 0, 1),
+      SIMD3<Int>(1, 0, 1),
+      SIMD3<Int>(-1, 1, 1),
+      SIMD3<Int>(0, 1, 1),
+      SIMD3<Int>(1, 1, 1),
+    ]
+}

Sources/Voxelotl/Common/ConcurrentDictionary.swift

@@ -62,6 +62,14 @@ public class ConcurrentDictionary<V: Hashable, T>: Collection {
       }
   }
 
+  public func take() -> Dictionary<V, T> {
+    self.locked {
+      let current = self.inner
+      self.inner = [:]
+      return current
+    }
+  }
+
   fileprivate func locked<X>(_ perform: () -> X) -> X {
     self.lock.lock()
     defer {

Sources/Voxelotl/Game.swift

@@ -87,8 +87,13 @@ class Game: GameDelegate {
 
     // Regenerate current chunk
     if regenChunk {
-      self.world.generate(chunkID: World.makeID(position: self.player.position))
+      let chunkID = World.makeID(position: self.player.position)
+      let chunk = self.world.generateSingleChunkUncommitted(chunkID: chunkID)
+      self.world.addChunk(chunkID: chunkID, chunk: chunk)
     }
+
+    self.world.generateAdjacentChunksIfNeeded(position: self.player.position)
+    self.world.update()
   }
 
   func draw(_ renderer: Renderer, _ time: GameTime) {

Sources/Voxelotl/Player.swift

@@ -8,7 +8,7 @@ struct Player {
     to: .init(Self.radius, Self.height, Self.radius))
 
   static let eyeLevel: Float = 1.4
-  static let epsilon = Float.ulpOfOne * 20
+  static let epsilon = Float.ulpOfOne * 2000
 
   static let accelerationCoeff: Float = 75
   static let airAccelCoeff: Float = 3

Sources/Voxelotl/World.swift

@@ -10,11 +10,14 @@ public class World {
   private var _chunks: Dictionary<ChunkID, Chunk>
   private var _chunkDamage: Set<ChunkID>
   private var _generator: WorldGenerator
+  private var _chunkGeneration: ChunkGeneration
 
   public init() {
     self._chunks = [:]
     self._chunkDamage = []
-    self._generator = WorldGenerator()
+    self._generator = StandardWorldGenerator()
+    self._chunkGeneration = ChunkGeneration(queue: .global(qos: .userInitiated))
+    self._chunkGeneration.world = self
   }
 
   func getBlock(at position: SIMD3<Int>) -> Block {
@@ -69,29 +72,26 @@ public class World {
     self._generator.reset(seed: seed)
     let orig = SIMD3(width, height, depth) / 2
 
-    let localChunks = ConcurrentDictionary<ChunkID, Chunk>()
-    let queue = OperationQueue()
-    queue.qualityOfService = .userInitiated
     for z in 0..<depth {
       for y in 0..<height {
         for x in 0..<width {
           let chunkID = SIMD3(x, y, z) &- orig
-          queue.addOperation {
-            let chunk = self._generator.makeChunk(id: chunkID)
-            localChunks[chunkID] = chunk
-          }
+          self._chunkGeneration.generate(chunkID: chunkID)
         }
       }
     }
-    queue.waitUntilAllOperationsAreFinished()
-    for (chunkID, chunk) in localChunks {
-      self._chunks[chunkID] = chunk
-      self._chunkDamage.insert(chunkID)
-    }
   }
 
-  func generate(chunkID: ChunkID) {
-    self._chunks[chunkID] = self._generator.makeChunk(id: chunkID)
+  func generateSingleChunkUncommitted(chunkID: SIMD3<Int>) -> Chunk {
+    self._generator.makeChunk(id: chunkID)
+  }
+
+  public func generateAdjacentChunksIfNeeded(position: SIMD3<Float>) {
+    self._chunkGeneration.generateAdjacentIfNeeded(position: position)
+  }
+
+  public func addChunk(chunkID: ChunkID, chunk: Chunk) {
+    self._chunks[chunkID] = chunk
     self._chunkDamage.insert(chunkID)
     for i: ChunkID in [ .X, .Y, .Z ] {
       for otherID in [ chunkID &- i, chunkID &+ i ] {
@@ -102,6 +102,10 @@ public class World {
     }
   }
 
+  public func update() {
+    self._chunkGeneration.acceptReadyChunks()
+  }
+
   func handleRenderDamagedChunks(_ body: (_ id: ChunkID, _ chunk: Chunk) -> Void) {
     for id in self._chunkDamage {
       body(id, self._chunks[id]!)

Sources/Voxelotl/WorldGenerator.swift

@@ -1,4 +1,9 @@
-struct WorldGenerator {
+protocol WorldGenerator {
+  mutating func reset(seed: UInt64)
+  func makeChunk(id: SIMD3<Int>) -> Chunk
+}
+
+struct StandardWorldGenerator: WorldGenerator {
   var noise: ImprovedPerlin<Float>!, noise2: SimplexNoise<Float>!
 
   public mutating func reset(seed: UInt64) {